The invention relates to control valves for fluid power actuators and methods for controlling flow to such actuators. More particularly, the invention relates to control valves and methods for controlling flow that utilize feedback.
In many circumstances it is desirable to control movement of a hydraulic actuator over a range of movement, for example by partially extending an actuator and holding it in place. Such partial extension may be accomplished by initiating hydraulic fluid flow to the actuator through a control valve, and by using information from an electronic sensor which senses the actuator position to determine when to shut off flow to the actuator.
However, electronic sensors are unsuitable for certain environments, such as where the actuator and the control valve will be subjected to high temperatures. Accordingly it will be appreciated that a means of accomplishing such partial actuation without use of electronic sensors would be desirable.
A control valve and a method of controlling fluid flow include an input device which provides an input for moving a primary valve member an amount which is a function of the input, thereby opening flow pathways through the valve. The control valve is connected to a mechanical feedback mechanism which moves a feedback valve member an amount which is a function of the movement of a device to which the fluid flow is directed, such as a hydraulic actuator. Movement of the actuator to a desired position causes the second valve member to be moved to such a position that, in combination with the first valve member, the flow pathways through the valve are closed. The actuator is thereby moved to and maintained at the desired position without the need for the electronic feedback sensor used in prior art systems to sense actuator position.
According to an aspect of the invention, a single-stage fluid flow cartridge control valve includes a cage having openings therethrough; a first valve member internally slidable within the cage; a second valve member internally slidable within the first valve member; and an input mechanism coupled to one of the valve members for moving the one of the valve members; wherein movement of the one of the valve members selectively opens fluid flow pathways between pairs of the openings, and movement of the other of the valve members selectively closes the fluid flow pathways. In a fluid actuator assembly, the other of the valve members is mechanically coupled to an actuator to which fluid is controllably supplied by the control valve.
According to another aspect of the invention, a fluid flow control valve includes a cage having openings therethrough; a first valve member internally slidable within the cage; a second valve member internally slidable within the first valve member, the second valve member having a bore therein and holes therethrough in communication with the bore; and an input mechanism coupled to one of the valve members for moving the one of the valve members; wherein movement of the one of the valve members selectively opens fluid flow pathways between pairs of the openings and movement of the other of the valve members selectively closes the fluid flow pathways, and wherein the holes and the bore are part of a fluid flow pathway between non-adjacent openings. Again, in a fluid actuator assembly, the other of the valve members is mechanically coupled to an actuator to which fluid is controllably supplied by the control valve.
According to a further aspect of the invention, a method of positioning a hydraulic actuator in response to an input signal includes opening flow pathways in a control valve by moving a main spool of the control valve a distance which is a function of the input signal; sending pressurized fluid to one side of the actuator, and draining fluid from the other side of the actuator, through the pathways; and closing the pathways after the actuator has reached a desired position by moving a feedback follower or spool which is mechanically coupled to the actuator.
According to a still further aspect of the invention, an actuator assembly includes an actuator for moving an external member, a control valve which controllably provides fluid to effect movement of the actuator, and a mechanical feedback device which provides actuator position feedback to the control valve.
In a preferred embodiment of the invention, the feedback valve member is internally slideable in and guided by a cage, while the primary or main valve member is internally slideable in the feedback valve member. This arrangement advantageously reduces or eliminates potential binding problems that might arise from side loads being applied to the feedback valve member by the feedback mechanism coupling the feedback valve member to the actuator. Further in accordance with a preferred embodiment, the input device or mechanism is an electric solenoid having the plunger thereof connected, preferably coaxially, to the primary or main valve member.
To the accomplishment of the foregoing and related ends, the invention comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.